In one aspect, this invention pertains to an olefin metathesis process wherein an unsaturated fatty acid ester or an unsaturated fatty acid is metathesized with a lower olefin in the presence of a metathesis catalyst to prepare a first product olefin, preferably, a reduced chain α-olefin, and a second product olefin, preferably, a reduced chain ester or acid-functionalized α-olefin. In another aspect, this invention pertains to a catalyst composition containing ruthenium or osmium.
The metathesis of unsaturated fatty acid esters or unsaturated fatty acids with a lower olefin can produce valuable α-olefins of reduced chain length. As an example, methyloleate or oleic acid can be metathesized with ethylene in the presence of a metathesis catalyst to prepare methyl-9-decenoate or 9-decenoic acid, respectively, and co-product 1-decene. The aforementioned products are α-olefins of reduced chain length, as compared with the chain length of methyloleate or oleic acid. α-Olefins find utility in the manufacture of poly(olefin) polymers. Ester-functionalized α-olefins can be readily hydrolyzed to the corresponding acid-functionalized α-olefins, which find utility in thermoset polymer applications, such as thermoset urethanes and epoxies. Alternatively, acid-functionalized α-olefins can be converted into acid-functionalized α-epoxides, which also find utility, for example, in the manufacture of epoxy resins. These utilities are especially applicable when the olefin functionality and the ester or acid functionality are located at the terminal positions of the carbon chain.
It is known to metathesize long chain olefins with ethylene in the presence of a metathesis catalyst to prepare terminally unsaturated hydrocarbons of medium chain length. In certain art, as disclosed, for example, in DD-A1-281594 (East German Publication), the metathesis catalyst is taught to comprise a tungsten (VI) halide, a tetraalkyl tin compound, and an organoaluminum compound. Disadvantageously, this metathesis catalyst requires three components and performs less efficiently with ester or acid-functionalized olefins, which features adversely affect the economics of the process. More disadvantageously, the tin component of the catalyst can leach into the metathesis product stream, thereby producing contamination problems in downstream applications. Similar olefin metathesis processes are known that employ an organorhenium oxide catalyst, as disclosed, for example, in WO 91/14665. Disadvantageously, the organorhenium oxide catalyst also exhibits instability in the presence of ester or acid-functionalized olefins, and also requires a tin co-catalyst for activation. As noted above, the tin co-catalyst can disadvantageously contaminate the metathesis product stream.
Metathesis reactions have also been disclosed, as illustrated, for example, by WO 96/04289, wherein an unsaturated fatty acid ester or unsaturated fatty acid is metathesized with an olefin in the presence of an organometallic catalyst comprising ruthenium or osmium bonded to a monodentate carbene ligand and other monodentate ligands. A monodentate ligand has one binding site to the metal atom or ion, for example, the ruthenium or osmium. Disadvantageously, this catalyst characterized by its monodentate ligands exhibits low activity and a slow metathesis reaction rate.
A more robust and recyclable ruthenium-based metathesis catalyst is known, as disclosed by Jason S. Kingsbury et al. in the Journal of the American Chemical Society, 1999, 121, 791–799, wherein ruthenium is bound to a chelating ligand containing a carbene moiety and a second electron donor moiety, both moieties being bound to the ruthenium atom. As described in detail hereinafter, a chelating ligand has two or more binding sites to the metal atom or ion. This catalyst, which is not bound to a catalyst support, is disclosed to catalyze the metathesis of styrenyl cycloalkenyl ethers to 2-substituted chromenes; but the reference is silent with respect to use of this catalyst in the metathesis of ester or acid-functionalized long chain olefins.
In view of the above, it would be desirable to discover a metathesis process wherein an unsaturated fatty acid ester or unsaturated fatty acid is metathesized with a lower olefin for the purpose of preparing product olefins, preferably, reduced chain α-olefins and reduced chain ester or acid-functionalized α-olefins. It would be more desirable if the metathesis process employed a metathesis catalyst that was less complex and less inhibited by ester and acid functionalities, as compared with prior art metathesis catalysts. It would be more desirable, if the olefin metathesis process employed a catalyst that did not substantially leach into the metathesis product stream and did not produce significant downstream contamination problems. It would be even more desirable if the metathesis catalyst was robust and recyclable, and exhibited good activity, even when anchored to a catalyst support. An anchored catalyst, by being heterogeneous, needs no complex separation and recovery from the reaction mixture, in contrast to a homogeneous catalyst, which by being dissolved in the reaction mixture requires more complex separation and recovery schemes. Finally, it would be most advantageous, if the olefin metathesis process operated efficiently with an improved reaction rate, as compared with prior art metathesis processes. All of the above properties would render the olefin metathesis process highly desirable for converting unsaturated fatty acid esters and unsaturated fatty acids to product olefins, preferably, reduced chain α-olefins and reduced chain ester or acid-functionalized α-olefins.